This chapter presents the recent advancements in environmental risk assessment methods for marine oil spills. A review is performed on the environmental hazards involved within accidental oil release and their associated risks. The fundamentals of the most important chemical and physical processes that occur during the oil spill have been presented along with an overview of the developments in oil spill modeling techniques. These processes result in a temporal and spatial change of oil concentration in the surrounding regions which in turn impose a substantial risk to the ecological entities present in the vicinity. A wide range of information is required for establishing the behavior of oil after release, hence this chapter reviews oil spill modeling data requirements. Upon demonstrating the environmental impacts resulted from several major historical accidents, this chapter concludes by reviewing important methods in oil spill environmental risk assessment methods.